The state of the art in such scales is comprehensively discussed in Chapter 7, entitled "Belt Scales", of "Weighing and Proportioning of Bulk Solids" by Hendrik Colijn and published by Trans Tech Publications in 1975. The content of this chapter is incorporated herein by reference. It will be apparent from a study thereof that the design of weighbridge systems for conveyors is associated with a number of problems.
The assignee of the present applicant is the proprietor of U.S. Pat. No. 4,157,661, issued June 12, 1979 to Milton R. Schindel, in respect of flowmeters of the inclined plate type, in which the inclined plate is supported by a load cell of the cantilever strain gauge bridge type. In improvements of this gauge disclosed in the same assignee's Canadian Pat. No. 1,104,371, improved forms of cantilever strain gauge bridge are employed. An earlier patent disclosing the use of cantilever strain gauge bridge units for measuring axle and drawbar loadings in vehicles is disclosed in U.S. Pat. No. 3,650,340 issued Mar. 21, 1972 to Bradley. In the flowmeter discussed above, a particular advantage of the use of cantilever strain gauge bridge units is the avoidance of the necessity for taking mechanical connections through the wall of the duct in which flow is being measured, whilst in the applications envisaged by Bradley, the insensitivity of the device to the lateral displacement of the load vector from the position of the wheel or drawbar is a great advantage.